Cap-reactor power groove ballast circuit

ABSTRACT

A cap-reactor power groove ballast circuit of the type including first and second, spaced-apart, elongated tape-like conductive foils having intervening layers of electrical insulation rolled together to form a compact cylindrical roll having combined capacitor-inductor-reactor characteristics. One of the spacedapart conductive foils has its width separated into multiple, electrically isolated, strip-like separate foil areas coacting with the common remaining conductive foil to function in the manner of multiple capacitor-inductor components electrically interconnected in circuit relationship. By appropriate connection of terminal tap points to the structure, the device can be made to operate in the manner of a power groove ballast circuit having improved wave shaping characteristics.

[ CAP-REACTOR POWER GROOVE BALLAST CIRCUIT [75] Inventor: Oliver H. Winn, Cazenovia, NY.

[73] 'Assignee: General Electric Company, Hudson Falls, NY.

[22] Filed: Mar. 27, 1972 [21] Appl. No.: 238,361

Related U.S. Application Data [62] Division of Ser. No. 91,674, Nov. 23, 1970, Pat. No.

[52] U.S. Cl. 336/69, 336/223 [51] Int. Cl. H0lf 27/28 [58] Field of Search 336/69, 223, 70, 336/165; 317/260, 256

[56] References Cited UNITED STATES PATENTS 3,191,103 6/1965 Segall 336/69 X 3,106,671 10/1963 Coleman et al 317/260 2,521,513 9/1950 Gray 336/165 X 3,093,775 6/1963 Lamphier 317/260 3,206,660 9/1965 McCutchen et a1.

1,795,411 3/1931 Sprague 2,000,441 5/1935 Given 317/260 X [451- Nov. 27, 1973 10/1935 Sprague 317/260 X 8/1951 Robinson 317/260 X Primary Examiner- Thomas J. Kozma Attorney-Nathan J. Cornfeld et a1.

[ 5 7] ABSTRACT function in the manner of multiple capacitor-inductor components electrically interconnected in circuit relationship. By appropriate connection of terminal tap points to the structure, the device can be made to operate in the manner of a power grooveballast circuit having improved wave shaping characteristics;

3 Claims, 8 Drawing Figures I 1 I136; F.

[2 ////////1 i l i 1.

6/1945 Great Britain 317/260 PATENTED HUVZ 7 I375 SHEET 1 UF. 2

F-IGLIVPRIORART,

PRIOR ART FIG.2.-

CIILZ BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to ballast circuit.

More particularly, the invention relates to a power groove ballast circuit fabricated in the form of a unitary (integral) combined capacitor-inductor-reactor (hereinafter referred to as a cap-reactor) having improved operating characteristics.

2. Description of the Prior Art A number of different cap-reactor devices which'exhibit combined capacitor inductor-reactor characteristics designed to operate in a number of different ways, are disclosed in U.S. Pat. No. 2,521,513 Gray Stationary Induction Apparatus issued Sept. 5, 1950. These known cap-reactor devices are suitable for a number of different circuit applications but can not be employed directly in a number of different equipment without requiring considerable modification. The present invention makes available anew and improved cap-reactor power groove ballast circuit for use as a starting and ballast circuit for fluorescentlamps and having improved operating characteristics.

SUMMARY OF THE INVENTION It is'therefore a primary object of the invention to provide a new and improved cap-reactor power groove ballast circuit.

Another object of the inventionis to-provide such a cap-reactor ballast circuit having improved. operating characteristics.

In practicing the invention,.a combined capacitorreactor device is provided which is of thetype including at least'first and second, spaced apart, elongated tape-like conductive foils having intervening layers of electrical insulation rolled together to form a combined capacitor-inductor-reactor. In the present invention a new and improved lamp the first conductive vfoil has its widthseparated into multiple, electrically isolated, strip-like separate foil areas coacting with the remaining'common second conductive foil to function in the manner of multiple capacitoninducto'r components electrically interconnected in circuit relationship.

The first conductive foil preferably is formed'into at least first and second electrically'isolated, separate foil areas of a size proportioned to provide'two different desired values of capacitance. First terminals means are connected to the first separatefoil areaand-second terminal means are connected to theremaining common first conductive foil on a side'thereof opposite'the point of connection of the first'terminal means to the first foil area both with respect'to the width and the length of the strip-like foil area. As a result,the capacitor-reactor devicefunctions as a parallel connected network of two series circuit branches each comprised by a series inductor and capacitor.

The second-terminal means is connected to the common second conductive foilatsome'point intermediate its width to thereby form an unconnected strip on' the .common second conductivefoil which does not contribute to the inductance of the'device. The first conductive foil only preferably has its width separated into at least first, second and third electrically 'isolated,

strip-like, separate foil areas with the third foil area being positioned opposite the unconnected strip of the common second conductive foil. Third terminal means are connected to the third separate foil area in ama'n ner such thatthe cap-reactor-device operates as though a third capacitor were connected in series circuit rela:

'tionship with the parallel connected series circuit braches,'and functionsin the manner of a powe'rgroove ballast circuit having improved wave shaping characteristics.

The device may be operated either as an air core device, or a magnetically permeable core member having a magnetic permeability greater than air may be positioned in the center of the roll of conductive foils and intervening layers of electrical insulation for increasing the value of inductance of the cap reactor device.

BRIEF'DESCRIPTION OF THE DRAWINGS Other objects, features and many of the attendant ad vantages of this invention will be appreciated more readily as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings wherein like parts in each of the several figures are identified by the samereference character, and wherein:

FIG. 1 is a perspective view of a partially disassembled coil or roll of tape-like, conductive foil having intervening layers of electrical insulation and rolled to form a cap-reactor device;

FIG. 2 is a schematic illustration of the structure shownin FIG. 1 if it were unrolled into a straight line structure, and depicts the manner in which the structure derives its capacitive characteristics;

FIG. 3 is a partial, cross sectional view of a capreactor power groove ballast circuit constructed'in accordance with the invention, and illustrates the relative proportions of the width of the conductive foils and conductive foil areas together with the point of connection of tap points or terminals to the conductive foils; FIG. 4 is an equivalent circuit diagram illustrating the details of circuit construction and manner of operation FIG. 6 is a perspective view of a completed capreactor power groove ballast circuit according to one form of theinvention; and v FIG. 7a and 7b are-a pair of'sketches illustrating critical dimensions of a cap-reactor device.

DESCRIPTION OF TI-IE PREFERRED EMBODIMENTS rial and the sheets of dielectric material 1-3 and14may comprise any known electrical insulating dielectric material 13 and 14 are rolled together to form a unitary or integral coil structure as shown in FIG. 1. While only one turn with two conductive foils 11 and 12 and suitable intervening insulating layers 13 and 14, are shownin FIG. 3, it is believed obvious that additional turns of foils and layers of insulation must be provided in order to obtain desired operating characteristics in the manner best shown in FIG. 5.

If the cap-reactorlO of FIG. 1 were unrolled and laid out flat, it would appear schematically as shown in FIG. 2 where S, and S represent the start of the tape-like conductive foils 11 and 12, and F and F represent the finish of each of the respective foils. When thus visualized, the manner in which the structure obtains its capacitive reactance characteristics can be more easily appreciated. Also, it is believed obvious from a consideration of the wound, interleaved, turns of the conductive foils 11' and 12 shown in FIG. 1 wherein the structure acquires its inductive reactance characteristics to thereby provide a combined capacitance-inductance reactance when employed in an electrical circuit.

In order for any given cap-reactor to be connected in electrical circuit relationship with the load, it must be specifically tailored ordesigned to serve that load. The particular cap-reactor described herein is specifically designed to serve as a power groove ballast circuit for a fluorescent lamp. For this purpose the device must serve to supply a high voltage surge across the lamp terminals for starting purposes as well as limit circuit current thereby ballasting the lamp since a fluorescent lamp while operating exhibits negative resistance characteristics. Prefereably, the ballast circuit should also exhibit high power factor characteristics for improved performance, and should not introduce undesired transients into the power supply lines with which it is used.

The power groove ballast circuit herein described is particularly designed to satisfy each of these requirements, in that it is intended for use with a single phase supply of alternating current, such as, a conventional, household, 60 cycle, 110-120 volt-l5 amp residential power supply used to energize other electrical appli ances such as television. sets, etc. For this reason, it is desirable that the loading effect of the ballast circuit not unduly distort the wave shape of the incoming alternating current supply.

FIG. 3 is a partial cross sectional view of a 'capreactor device constructed in accordance with the invention and intended to operate as a cap-reactor power groove ballast circuit. It should be expressly noted that FIG. 3 is a cross sectional view that is transverse to the elongated or long dimension of the strip-like conductive foils (and hence transverse to the view shown in FIG. 2), and illustrates the manner in which the width of the conductive strips is proportioned (as well as the manner of connection thereto) to provide the desirable characteristics enumerated above in a single (integral) cap-reactor device. In FIG. 3, one of the conductive foils (for example 11 hereinafter referred to as the first conductive foil) has its width separated into multiple (3), electrically isolated, strip-like'separate foil areas 1 1 11 and 11 During fabrication the respective separate foil areas 11 11 etc. can be formed by securing an integral foil such as shown at 12 to one side of the dielectric layer 13, and thereafter etching away undesired portions of the foil througha suitable foil-resist and chemical etching steps to leave a composite structure comprised by the insulating layer 13 and the multiple electrically isolated strip-like separate foil areas 11 11 etc. The composite: structure thus obtained, may then be wound together with the remaining second conductive foil 12 (which is integral across its width and hence is common to all of the separate foil areas 11 11 etc.) together'with the required intervening insulating layers 13 and 14 (not shown in FIG. 3). As-

will be described more fully hereinafter, the width of the conductive foil 12 and separate foilareas 11 11 etc; thenumber of turns in the rolled cap-reactor device, the mean radius of the roll or other comparable dimensions, the radial thickness of the roll, the dielectric constant and the thicknesspf theintervening-inswv lating layers 13 and 14, all are proportioned to'p rovide a desired value of inductance and capacitance. In order to obtain increased values of inductance with the capreactor device it may prove desirable to include a magnetic permeable core member such as shown at 15 hav ing a magnetic permeability greater than air. This core member is positioned in the center of the roll of conductive foils and intervening layers of electrical insulation as will be described hereinafter in connection with FIG. 4 and serves to increase the value of inductance of the cap-reactor device.

In addition to the width and length (area) of the respective conductive foils-(and foil areas) an important parameter adjusting feature is obtained in the capreactor device by means of the point of connection of terminal tap points such as shown at one, two, three,

-the common second conductive foil'"12 opposite the input terminal tap point four with respect to both the width as shown in FIG. 3 and the length of the foil as depicted by FIG. 2. For example, referring to FIG. 2,

if the point F is assumed to constitute the input termi- *1.

nal tap point four, then with respect to the length of the conductive foil, the point S, (or some intermediate point along the length depending upon the value of inductance desired) would be chosen as the output terminal tap point two. 4

It should also be noted that the second terminal tap point two is connected to the common second conductive foil 12 at a point intermediate its width to thereby form an unconnected strip indicated at 12,, on the common second conductive foil 12. As will be explained more fully hereinafter'this unconnected strip 12,, does not contribute to the inductance of the capreactor device, but acting in conjunction with thethird conductive foil area 11 does form a third capacitor which is serially connected in circuit relationship in the manner shown in the equivalent circuit diagram illustrated in FIG. 4 of the drawings. FIG. 4 of the drawings of a transformer and hence is suppliedfrom the secondary output winding of an 'input power supply step-up transformer 17 whose primary winding is supplied from a conventional -1l0 .volt, 6O cycle alternating current residentialsourc'e of electric energy. A pair of fluores- 'cent lamps shown at 18 and 19 are connected in series circuit relationship across the output secondary winding 17, through the cap-resistorpowergroove ballast circuit by connecting one end of the series connected fluorescent lamps l8 and 19 to the terminal tap point number two. FIG. of the drawings shows the nature of the physical connection to the tap two through the medium of output terminal T The remaining endof the series connected fluorescent lamps 18 and 19 is connected back to the lower end of the secondary winding 17,. The upper end of the secondary winding 17, is connected through the input terminal T to the terminaltap point four as shown in FIG. 5. The terminal tap point three is connected through terminal T to the juncture of the fluorescent lamps l8 and 19 thereby serving to connect the'c'apacitor C formed by the conductive foil area 11 in conjunction with the unexcited strip 12,, to the juncture of the fluorescent lamps as best shownin the equivalent circuit diagram in FIG. 4.

As best shown in FIG. 4, the plurality of conductive foil areas 11 11 and 11 acting in conjunction with the common second conductive foil 12 forms three capacitors C C and C These capacitors in effect are connected in electrical circuit relationship with the inductances L, and L exhibited by the cap-resistor device as a consequence of the flux linkage between the multiple turns of the device. The value of these capacitances and inductances is determined by the width of the foil areas acting in conjunctionwith the common second conducting foil, the number of turns in the roll, the mean radius of the roll or other comparable dimensions, the radial thickness of the roll, the dielectric constant and the thickness of the intervening layers of electrical insulation as set forth in the following equations. In these equations, it has been assumed that the rolled cap-reactor device is either round or flattened. If it is round, it will have a mean radius R measured from the center of the arbor hole in the device, and if flattened, it will have an elongated arbor hole or center slit of length S. Also, with a flattened roll, it will have a roll thickness T. With either type of construction, the roll will have a radial build as depicted in FIGS. 7a and 7b of the drawings. The value of capacitance and inductance is given by the following equations:

c,= 5.4 kW/d) 1) Wherez' C,= Capacitance farads k Dielectric Constant W Width inches d Thickness of dielectric inches 5 Where:

L Inductance microhenries N Number of turns v W Width of foil inches R mean Radius inches 10 a Radial build inches 15 Where L Inductance microhenries W= Width of foil inches T= Length of pad inches S Lenght of center slit inches 0 a Radial build inches 25 the fluorescent lamps l8 and 19 and thereafter to limit current flow through the lamps and ballast their negative resistance characteristics while lighted. In operation, the inductor L and series capacitor C, operate in the normal manner of a choke and surge capacitor for providing the starting surge and current limiting functions'. The parallel connected s'e'ries circuit branch comprised by the inductor L and series. connected capacitors C functions as a compensating coil and capacitor for improving the wave form characteristics of the 5 overall circuit arrangement. The capacitor C provides the desired power factor improvement.

Referring again to FIG. 5, it will 'be noted that the core member 15 is shown in dotted outline form. This has been done to indicate that the magnetically permeable core member 15 maybe included if desired, or alternatively the device may be operated as an air core device. If the core member 15 is included, it will increase the value of the inductance L so that the capacitance of the series connected capacitor C should be correspondingly increased. In one known embodiment, the parameters of the cap-reactor were adjusted so that the value of the inductance L were approximately 22 millihenries and the capacitor C had a value on the order of 0.028 microfarads. In the event that the magnetically permeable core member 15 is employed, it may comprise a single steel lamination about 1 inch wide by 0.014 inches in thickness and having a length such that its ends protude beyond the ends of the roll capacitor 10 and can be bent together in overlapping closed magnetic circuit relationship ,in the manner shown by 15a and 15b in FIG. 6' of the drawings. Other types of core structures could of course be employed; however, the single lamination core fabricated in the above manner is desirable due to its low cost. The completed cap-reactor would appear as shown in FIG. 6 of the drawings wherein T T etc. constitute the input and output terminals to the device. Due to the fact that I in many circuit applications an input terminal will not be required to the tap point one, it is of course obvious that the input terminal T could be eliminated 'w'li'ere the device is to be employed in the manner depicted in FIGS. 4 and 5. However, the input terminal T, has been device for use in circuit applications where illustrated to show the general utility of the cap-reactor it is desired to connect to the tap point one.

It has been determined also that a cap-reactor ballast circuit according to the invention can be built using an air core. When thus employed, the inductance L may have a low value on the order of 0.25 millihenries which is almost 100 times less than the inductance required if an iron core is employed. With such an arrangement, the value of the capacitance C should be comparably lower on the order of 0.18 micro farads. It appears that this reduction in capacitance coupled with the lower value of inductance accomplishes the same wave forming characteristics as does the higher valued iron core structure. The amount of inductance required to accomplish the desired wave forming; however, is determined by a particular cap-reactor design used for a specific circuit application.

In addition to the above considerations, it should be noted in FIG. 5 that additional volume for the rolled cap-reactor is indicated by the dotted outline structure. This dotted structure has not been shown in detail since it would be identical to the two turns of the rolled conductive foils and the intervening layers of insulation shown in FIG. 5. It is of course anticipated that any desired number of turns may be employed in fabricating the device depending upon the values of inductance and capacitance required. It should be noted also that if more turns than those shown are employed, the tap off points two and three would be moved to corresponding points on the outermost turn as will be obvious to one skilled in the art in view of the above teachings.

From the foregoing description, it will be appreciated that the invention provides a new and improved power groove ballast circuit fabricated in the form of a unitary (integral) combined capacitor-inductor-reactor having improved operating characteristics.

Having described several embodiments of a new and improved cap-reactor power groove ballast circuit constructed in accordance with the invention, it is believed obvious that other modifications and variations of the invention are possible in the light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments of the invention described which are within the full intended scope of the invention as defined by the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In a combined capacitor-reactor device of the type including at least first and second, spaced-apart, elongated tape-like conductive foils from intervening layers of electrical insulation rolled together to form a combined capacitor inductor-reactor, the improvement comprising a. only the first conductive foil having its width separated into first, second and third electrically isolated, strip-like separate foil areas coacting with connected to the first separate the point of connection of the first terminal means 1 to the first foil area relative to both width and length, whereby the capacitor-reactor device functions as a parallel connected network of two series circuit branches each comprised by a series connected inductor and capacitor,

d. the second terminal means being connected to the common second conductive foil at some point intermediate its width to thereby form an unconnected strip on the common second conductive foil which does not contribute to the inductance of the device,

e. the third foil area being positioned opposite the unconnected strip of the common second conductive foil,

f. third terminal means connected to said third separate foil area whereby a third capacitor is connected in series circuit relationship with the parallel connected series circuit branches,

g. an input fourth terminal means on said second foil area of the first foil, and

h. a magnetically permeable core means having a magnetic permeability greater than air positioned in the center of the roll of conductive foils and intervening layers of electrical insulation for increasing the value of inductance of the combined capacitor-reactor device.

2. A combined capacitor-reactor device according to claim 1 wherein the core member comprises a single steel lamination inserted in the arbor hole of the rolled foils and intervening insulating layers and having the ends thereof projecting .beyondthe width of theroll bent together in overlapping closed magnetic circuit relationship. a

3. A combined capacitor-reactor device according to claim 1 wherein the single steel lamination is on the order of one inch wide by 0.014 inches thick, and the width of the common second conductive foil and-sepa the order of 0.28 microfarads whereby the power groove ballast circuit has improved wave shaping characteristics.

Patent No.

UNHED STATES PATENT ()FFEQE EC'HQN D t Novembef 27, 1973.

Inventofls) Olivier H, Winn It is ce rtified that ex rbr apipaars in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

:9, changa bmches" t9 branches 16, thange "resistor" to reactor 39, change "resiswr" to reactor 6 0, delete before 5 and fihe af tgr d 2, cielet "I before -midi the "1 after a aha imlge;1.

change mg;

"0" before th a "Length" to Thickfiess "Lenght" to Length "wm'e" to was means to mean (SEAL) AW??? EDWARD IIVLFLETCHERJRQ Attestin Officer "c MARSHA-LLE DANN 7 7 Commissioner of Patents P0405) STATES P mew @FFEC'E CERTAFECAAE CW ERRETEN P t t N 3, 77%,720 D November 27, 1973 Inve tm-( Oliver Winn It is certified that error appears in. the ebove-identified patent and that said Letters Patent hereby enrreeteci as shown below:

Column 2, line 9, change braehee branches Column 5, line ii-5 change resistor to reactor Column 5 line 39 change register to reactor n Column 5, line 60, delete bQIEOTf 5 and the after (1 Column 6, line I 2 eeleee E before IL en the W after a Column 6, line 12, "0" before the w a a Column 6, line 18 change Length 6:0 Thielmess Column 6, line 19, change "Lenghe" co Length Column 6, line 42-7, change "weae" to was C Column 6, line &9, change @0028 to ,28

Column 8 line w, change "meens (to u mean Signed and sealed this 9th day of April 197M.

(SEAL) Attest:

EDWARD I LFLETGHER JRO C Q MARSHALL DANN Attesting Officer Commissionerof Patents 

1. In a combined capacitor-reactor device of the type including at least first and second, spaced-apart, elongated tape-like conductive foils from intervening layers of electrical insulation rolled together to form a combined capacitor-inductor-reactor, the improvement comprising a. only the first conductive foil having its width separated into first, second and third electrically isolated, strip-like separate foil areas coacting with the remaining common second conductive foil to provide different capacitances and to function in the manner of multiple capacitor-inductor components in electrically interconnected circuit relationship, b. first terminal means connected to the first separate foil area, c. second terminal means connected to the common second conductive foil on the side thereof opposite the point of connection of the first terminal means to the first foil area relative to both width and length, whereby the capacitorreactor device functions as a parallel connected network of two series circuit branches each comprised by a series connected inductor and capacitor, d. the second terminal means being connected to the common second conductive foil at some point intermediate its width to thereby form an unconnected strip on the common second conductive foil which does not contribute to the inductance of the device, e. the third foil area being positioned opposite the unconnected strip of the common second conductive foil, f. third terminal means connected to said third separate foil area whereby a third capacitor is connected in series circuit relationship with the parallel connected series circuit branches, g. an input fourth terminal means on said second foil area of the first foil, and h. a magnetically permeable core means having a magnetic permeability greater than air positioned in the center of the roll of conductive foils and intervening layers of electrical insulation for increasing the value of inductance of the combined capacitor-reactor device.
 2. A combined capacitor-reactor device according to claim 1 wherein the core member comprises a single steel lamination inserted in the arbor hole of the rolled foils and intervening insulating layers and having the ends thereof projecting beyond the width of the roll bent together in overlapping closed magnetic circuit relationship.
 3. A combined capacitor-reactor device according to claim 1 wherein the single steel lamination is on the order of one inch wide by 0.014 inches thick, and the width of the common second conductive foil and separate foil areas, the number of turns in the roll, the means radius of the roll or other comparable dimension, the radial thickness of the roll, the dielectric constant and the thickness of the intervening layers of electrical insulation all are proportioned to provide a compensating inductance on the order of 22 millihenries, and a series connected compensating capacitance on the order of 0.28 microfarads whereby the power groove ballasT circuit has improved wave shaping characteristics. 